There have been a number of questions, regarding the RadEditor for MOSS and whether it is possible to use it in the SharePoint 2007 Wiki libraries and sites. The short answer to this question is - yes it's possible. Here is the long version: Wiki pages in MOSS 2007 are stored as normal document libraries. This means that when you edit a Wiki page, you are actually editing a list item. RadEditor for MOSS supports this scenario and you can use it to replace the default editor in all major browsers - Internet Explorer, Firefox, Safari, etc.
Here is how to activate the RadEditor for MOSS list items (the same guide is available in the RadEditor for MOSS documentation topic
Using RadEditor in List Items):
1. You need to get the latest build of our editor. Go to this page for more info and download details -
http://www.telerik.com/products/sharepoint/overview.aspx
2. Install the RadEditor for MOSS in your web farm. Installation instructions are available in the documentation, which comes with the download.
3. Browse to the SharePoint site which, where you want to use the RadEditor in list items and open the Site Settings page. From the Site Settings, navigate to Site Features.
4. Activate the RadEditor features. You can use the editor in all browsers, or you can leave the default rich text editor in Internet Explorer and use ours everywhere else. Here is a screenshot with the RadEditor features:
5. You might need to restart IIS to recycle the SharePoint web application. This step is required since MOSS will cache the default editor the first time it is used.
6. That's it. You can now use RadEditor for MOSS to edit Wiki pages in your site. Remember that the RadEditor features are local to the site, so if you want to edit list items in a different site, you need to redo steps 3 and 4 for it.
After you have our editor up and running, you might want to customize its appearance/options. You can do that with the editor's tools and configuration files. By default, they are located at \Program Files\Common Files\Microsoft Shared\web server extensions\wpresources\RadEditorSharePoint\4.1.0.0__1f131a624888eeed\RadControls\Editor\ (where 4.1.0 represents the installed editor build). The files you need to modify are called ListToolsFile.xml and ListConfigFile.xml.